Semiconductor technologies are developing very fast, especially semiconductor dies have a tendency toward miniaturization. However, the requirements for the functions of the semiconductor dies have an opposite tendency to variety. Namely, the semiconductor dies must have more I/O pads in a smaller area, so the density of the pins is raised quickly. It causes the packaging for the semiconductor dies to become more difficult.
The main purpose of the package structure is to protect the dies from outside damage. Furthermore, the heat generated by the dies must be diffused efficiently through the package structure to ensure the operation the dies.
As known in the art, a wafer level package (WLP) packages the dies on a wafer before dividing the dies into respective dies. The WLP technology has some advantages, such as producing a shorter cycle time and lower cost. Fan-out wafer-level packaging (FOWLP) is a packaging process in which contacts of a semiconductor die are redistributed over a larger area through a redistribution layer (RDL) that is typically formed on a substrate such as a TSV interposer.
The RDL is typically defined by the addition of metal and dielectric layers onto the surface of the wafer to re-route the I/O layout into a looser pitch footprint. Such redistribution requires thin film polymers such as BCB, PI or other organic polymers and metallization such as Al or Cu to reroute the peripheral pads to an area array configuration.
The TSV interposer is costly because fabricating the interposer substrate with TSVs is a complex process. Thus, forming FOWLP products that includes an interposer having a TSV interposer may be undesirable for certain applications.
In wafer level packaging, the wafer and the dies mounted on the wafer are typically covered with a relatively thick layer of the molding compound. The thick layer of the molding compound results in increased warping of the packaging due to coefficient of thermal expansion (CTE) mismatch and the thickness of the packaging. It is known that wafer warpage continues to be a concern.
Warpage can prevent successful assembly of a die-to-wafer stack because of the inability to maintain the coupling of the die and wafer. Warpage issue is serious especially in a large sized wafer, and has raised an obstacle to a wafer level semiconductor packaging process that requires fine-pitch RDL process. Therefore, there remains a need in the art for an improved method of manufacturing wafer level packages.